Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

[Jonny Accelerant]

I've done some research and this appears to be a classic problem. There are other threads where there are recommendations for what capacitor to replace C504 with. My primary question is if that conventional wisdom is still the same, or has it changed. Have there been advances in "capacitor technology" such that there is a better replacement cap available? From what I've read, this cap is subjected to very high voltages and that is the reason for it chronically burning-up, so if there is a way for me to maybe spend a few dollars and make certain it never happens again, I'd be interested.

Secondary to that, on visual inspection on the "power" pc board, I note that resistors R508 (near C504) and R525 (on the other side of the pc board) are both discolored, and I wonder if they should be replaced also, as a preventative. Does discoloration of a resistor necessarily mean overheating, and does overheating cause permanent damage, i.e. a change in resistance value and/or a decrease in life-expectancy, and with all of that in mind, is it worth the time & trouble to replace them, as long as I have the guts of this LCD monitor exposed?

As always, any help appreciated and thanks in advance.

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

You can go with higher rating voltage, it will be bigger so you will have to bend the legs to fit into the board. These cap are hard to get.

[SteveNielsen]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Resistors emit heat and that discoloration is not abnormal in and of itself. Check the resistor value and the solder joints on the other side of the board.

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Rather than wait around and try to be spoon-fed, I rolled the dice and purchased these:

http://www.ebay.com/itm/151241533512...%3AMEBIDX%3AIT

The vendor is right in San Antonio, so shipping time was a big factor in the decision. Plus the price is right. 10 caps for $13.00, I could probably sell the remaining 8 for $5.00 each and make some money. Or I could be nice and give them away to a BadCaps member that needed them.

Interested in finding out if this was a mistake or not. Gave Digi-Key a fast look-through and it seems these high-voltage, ceramic caps are rare, so I decided to stay inside the lines and go the eBay route, but if someone wants to make a specific recommendation for what might have been a better choice, maybe it will help someone else. Or me, if these caps fail to work or burn up shortly after being installed.

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Your board uses 5pF?
http://s807.photobucket.com/user/bud...?sort=3&page=1
Fixed many of these models and other inverter with bad ballast caps. I use 6300V very hard to get.
Ceramic caps failed in shorted or high leakage mode..

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

I read something earlier today and just confirmed it visually, which is that there is a symetry to this board. and the C504 cap has a match on the other side, but I've never seen the other side's "matching" capacitor ever go bad. I've only seen pics of C504 being bad.

So, assuming that the symetry of components means an equal share of whatever power that they are supplying, why is one side going bad and the other is, apparantly not?

So, while doing research on this question, I've not found a way to definitively identify this power board. Other monitors I've read about have an "x" board, and everyone seems to be familiar with "x", but I've not seen a post where a knowledgeable person comments with any sense of "named" faminliarity with the board. Ran Google searches of all the text on the board, and none of those were definitive either. Most cross-referenced to the LCD monitor's model number, but only for purposes of marketing, and not for the purpose of manufacturing.

I get the impression that this board is a custom-created, for one model LCD monitor only, and the manufacturer made the decision to not even give it a durable name, either that or it was made once and never again, and that is why I can't find any real common body of documentation on the whole board; only the single capacitor is mentioned, and as I've mentioned, not it's matching "pair" on the other, (assuming it's a) parallel circuit.

So, anyone familiar with this thing? I'm asking because with a handful of extra caps, it might be a good idea to see what other LCD monitors they can be used to repair. At this point, I can only find the one single LCD monitor that I have, the LP2626. Maybe it was so badly designed that no one else has ever used it? Or maybe there's a ton of them (LCD monitors using this prone-to-defect board) out there, but no cross-referencing documentation?

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Those caps can be used for other repair, it can be used in parallel to get 10pf if the circuits needed: for example
https://www.badcaps.net/forum/showth...5PF#post305177
If you plan to do more repair, I would keep them.

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Your board uses 5pF?
http://s807.photobucket.com/user/bud...?sort=3&page=1
Fixed many of these models and other inverter with bad ballast caps. I use 6300V very hard to get.
Ceramic caps failed in shorted or high leakage mode..

CRAP. NO.

N3 3KV SEC
12J 3KV JNC

Alright, I just sent the ebay vendor a message trying to cancel the order. And I'm going to slow down and ask for help. I'm trying to get this and several other things done all at the same time and nothing is getting done and I'm making a big mess.

Do you have a recommended part number for these caps? The 12J 3KV JNC cap is burnt. Might as well replace all 4 of them.

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

12pf, this is what I use:
http://www.mouser.com/ProductDetail/...1IlTe5LtlVc%3d
3pf is just about impossible to get.
BTW, if you look at the cap, it is connected right across the high voltage winding, exactly why (part of the tuned out put?) I do not know but it is really tough for the cap, it is not being used as ballast cap (in series with the lamp to limit lamp current).

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

How about this one:

http://www.digikey.com/product-detai...191-ND/1021839

or this:

http://www.mouser.com/ProductDetail/...0LsS%2fqhbo%3d

is rated to 6 Kv. Better, right?

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

3pf:
http://www.mouser.com/ProductDetail/...zlflv4s41XU%3d

I would go for the TDK 12PF 6KV from MOUSER which will be obselete soon (end of life), the one you posted:
http://www.mouser.com/ProductDetail/...0LsS%2fqhbo%3d

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

12pf, this is what I use:
http://www.mouser.com/ProductDetail/...1IlTe5LtlVc%3d
3pf is just about impossible to get.

BTW, if you look at the cap, it is connected right across the high voltage winding, exactly why (part of the tuned out put?) I do not know but it is really tough for the cap, it is not being used as ballast cap (in series with the lamp to limit lamp current).

Well is it possible the design is in error? Earlier in the thread I asked about this "symmetry" thing, and why it is that this particular cap goes bad, but it's "match" on the other side of the pc board does not. What if someone made a "typo" and "matched" this cap when it's not part of a parallel circuit?

I read something earlier today and just confirmed it visually, which is that there is a symmetry to this board. and the C504 cap has a match on the other side, but I've never seen the other side's "matching" capacitor ever go bad. I've only seen pics of C504 being bad.

So, assuming that the symmetry of components means an equal share of whatever power that they are supplying, why is one side going bad and the other is, apparently not?

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

It is uses two transformers so the circuits are exactly the same. both 12PF are connected in parallel with high voltage transformers, I have seen the same set up used in Viewsonic and Dell, and HP inverter board as well.

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

It is uses two transformers so the circuits are exactly the same. both 12PF are connected in parallel with high voltage transformers, I have seen the same set up used in Viewsonic and Dell, and HP inverter board as well.

The circuit diagram on the left specs that cap at 15 pF and 3KV, and the diagram on the right specs the cap at 10 pF and 6KV, and the LP2626 is spec'd at 12pF and 3KV.

Would the LP2626 be better off with a higher capacitance, higher max volt capacitor, since by these two diagrams it seems that there's a bit of inverse relationship between capacitance and max voltage, and maybe one reason for the failure is that they went lower in capacitance (than 15 pF) but not higher in max voltage. In this specific circuit, could a 15 pF, 6KV capacitor improve the overall design?

Also, earlier today I was reading a .pdf (you posted?) about ESR: Fact or Myth or words to that effect and while a lot of it went past me I understood that the performance of these low-ESR caps is going to change on frequency and that in the application of (computer) power supplies, the low-esr caps can cause some kind of voltage oscillation in the output of the PSU due to (assuming here) some unique quality of the circuit that causes bad things to happen at certain frequencies. Then the anecdotal example of how a low-ohm resistor in series with the low-esr cap suddenly made this oscillation go away.

So, since this is a bit of a PSU, creating power, etc... what if this cap is going bad due to "oscillation" that spikes the voltage higher than it's rated (3KV) value, but only sometimes, at certain frequencies. Solution increase the max voltage, add a resistor or increase the capacitance (somewhat) to change the "sweet spot", the point at which the oscillation occurs?

How'm I doing?



And also (PS) the symmetry of the circuit again prompts me to ask why only C504 goes bad, and not C519 (it's "match"). Also if the LP2626 is like the circuit diagram you attached, they seem to be in series, which seems odd to me. Why 2 caps in series and not one big cap? Is there a name for that special technique?

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

"The circuit diagram on the left specs that cap at 15 pF and 3KV" They are connected in series so effectively capacitance is 7.5pF across the winding and voltage breakdown of 6KV.
The one on the right is single 10pf cap rated at 6KV, so the Vizio should have use 6KV cap to begin with.
Bascialy, the value of the cap is between 7pF~12pF.
I would say the failure is due to using 3KV instead of 6KV, the spike can be more than 3KV.
Of the 10 LP2626 I repair, 3 of them had failed 12pF cap in the another inverter transformer.
BTW, the circuit on the left is pretty close to what is used in the LP, you can also see caps C826 (5pF), C827 (5pF) connected in series so the capacitance is 2.5pF for the sensing circuits.

[Jonny Accelerant]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Of the 10 LP2626 I repair, 3 of them had failed 12pF cap in the another inverter transformer.

Is there any "electronic" reason why one capacitor is more likely to fail than the other? (30% vs. 50%)?

Also, FIW I found this, which seems to show the same power board is used on a "FujitsuSiemens SL3260":

https://www.badcaps.net/forum/showthread.php?t=30464

I keep hoping to find a name for this board that is something other than the official Vizio part number, as I suspect it's more common than just these one or two LCD monitors.

[budm]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

I am sure that PCBA is used by more than one OEMs. Vizio does not actually make the TV, most of there TV are made by AmTran which also makes TVs for other companies., then AmTran will also by PCBA from other OEMs such as Delta Electroincs for the power supplies, the Inverter and T-CON PCBA most of the the time are part of the LCD panel assemblies.
http://en.wikipedia.org/wiki/Vizio
When I was in China for business trips, I went to the electronics bazaar, you can build your own LCD TV by buying the kits.
http://www.alibaba.com/product-detai...683530933.html
http://www.alibaba.com/product-detai...561919922.html
http://www.alibaba.com/product-detai...734169373.html

All you have do then is to put your company name on it.

[Jonny Accelerant]

Success !!

I'm pleased to report that the repair is a 100% success. The 4 capacitors arrived today from Mouser, and only took 3 days to arrive. About $11.00 total, most of which was shipping, and that was the cheapest option.

This is monitor, lessee... #3? #4? for me and so things went smooth, MOST PARTICULARLY since I invested in a desoldering iron from Radio Shack ($15.00). I got the kind that has the squeeze bulb above the iron. Did such a good job that on the 2nd lead's solder removal, the capacitors all just fell out.

The biggest issue I had was reassembly as the power and signal components are actually TAPED to the back of the LCD panel and it's the back cover that aligns them, so if you tape it too tightly, the back cover can't "scooch" (move around) the two interior compartments, so I didn't tape it at all. Seems to be okay. Cable routing took longer than desoldering and soldering. What a pain in the #@)$(. But monitor fired right up and looks great.

I'd like to thank everyone that helped in this thread (and those previous), most particularly Budm on the electronics theory and parts recommendation. See attached photos of the work.

[re-atari]

Re: Success !!

I'm pleased to report that the repair is a 100% success.

I'd like to thank everyone that helped in this thread (and those previous), most particularly Budm on the electronics theory and parts recommendation. See attached photos of the work.

Good job, glad my story was of help to you. My SL3260 is still going strong after the repair I described in the thread you linked to in post 16. If one or both HV caps fail again I'll replace them with 12pF 6kV ones.

re-atari

[jdwinty]

Re: Vizio LP2626/VMM26-F20I, C504 Burnt: What about R508 & R525

Hey, I just wanted to thank all you guys for being here and posting all this wonderful information. I am but a novice, but with the information on here I was able to buy the right capacitors, solder them in (only my second PCB repair) and my Visio 26in monitor is now working better than ever. Again, Thank you so much!